Now that I feel a little silly after LEMV failed to deliver near it's capabilities in terms of endurance, I have felt somewhat skeptical of airship designers claims lately. One such claim by currently trending worldwide Aeros corporation is that their Aeroscraft will be able to takeoff vertically with maximum payload on all versions. I can tell you already this is one claim I would not relay on, it's probably an embellishment of the facts, a little white lie to sell the Aerocraft to investors. Like maybe it can take off vertically with max payload, but only under the condition of little or no fuel, which is probably closer to the case I'm thinking.
The claim on their website that the Aeroscraft could takeoff vertically with 500 tons is the one that sounds really fantastic, I just can't imagine them putting an engine on it that's powerful enough to lift that much weight without being too heavy itself. According to what I have read in the media, the Pelican's (Dragon Dream) internal bouncy system is only able to displace 2,000- 4,000 pounds of lifting capability. That indeed dose make it revolutionary in terms of airship technology, but I have now learned from Russia Today that the Pelican only has 365 horsepower engines for a combined total of 1095 horsepower. If the Pelican is indeed only half the size of the ML866 and has a maximum lifting capacity of 10 tons, this makes it possible to take off vertically but just barely. The ML866 and ML868 could take off with maximum payload and some fuel, but the ML86X taking off with Max payload would need 54,740 combined horsepower.
That's just about half the horsepower of this diesel engine which weighs in at 2,300 tons. So if the engines are diesel which makes sense for airships, that's about 1,150 TONS of engine! Twice what the specification's claim it's cargo capacity is, and we are not factoring in the weight of fuel or the weight of the frame. the Pelican's weighs about 16 tons including engine weight. So scaling that up by 50, the ML86X should weigh in at 800 tons with engines. Now aviation diesel engines are lighter then marine diesel engines. The best diesel aviation engine I have heard about can give 500 horsepower and only weighs 800 pounds, so if we scale that up to meet the demands of the ML86X that gives us only 44 tons of engine now, which makes the job very double, but what are the complications in making an aviation diesel engine that can deliver 18,247 Horsepower and only weighs 6 tons? Can it even be done today? This dose not sound like an easy engine to make, and realistically I imagine the real weight of the engine will come in somewhere between these two extremes. So the average of these two numbers is 597 tons, and taking into consideration that the engine will fall more into aviation diesel category rather then the marine diesel category, lets say the engine weight of all engines will come in at around 300 tons.
With this weight we figure the frame weighs about 500 tons, the engines weighs 300 tons, and it can take off vertically with 500 tons. That is again, very difficult, but possible. However now the problem is fuel. These engines are going to consume huge amounts of fuel, especially in a maximum throttle vertical takeoff, or hover. So while it's all well and good if you want to hover for 3 minutes with 500 tons, but how much fuel are you going to need to hover for 20 minutes? An hour? Even if we imagine that it's getting the great rate as that diesel engine I posted above, that gives us 1696.94 gallons of diesel fuel consumed per hour, or 6 tons of fuel per hour at 75%. Now in a hover the engines will need to be at or very close to maximum output. That means we can estimate an extra 66% fuel consumption rate or 9.1 tons of fuel consumed per hour in a hover. That's not a deal breaker, yes it will be able to hover with 500 tons, but how much of the weight is going to need to be fuel?
The claim on their page is that the ML86X will be able to take 500 tons, 5,300 nautical miles at a speed of 100 knots. That means the ML86x will spend 53 hours to get there and use 318 tons of fuel! There is no way it's going to be able to take of vertically with that and 500 tons, and 800 tons of airship, it's just not possible. It might be able to take off, but it will need to take off conventionally, without VTOL. Which is probably where the embellishment of the facts rests.
This page makes it seem like the Aeroscraft can take off with full VTOL, at full payload and go maximum range, which unless the engines do come in at 44 tons, this is simply untrue. You can ether take 500 tons, 5,300 nautical miles without VTOL, or you can hover 500 tons of cargo for a few hours, not both.
Ultimately I'm sure this also applies to the ML866 and 868, but to a lessor degree as smaller airships benefit more from aerodynamic lift.
I think you're depending too much on the variable buoyancy figures from the prototype in your arguement. I doubt they are spending a lot of money on the pumps and tanks used in the test vehicle, so I would expect the efficiency to increase several orders in the finished product. Plus the prototype is only about 240 feet long and the 500 ton version will be at least 4 times longer than that which would increase the volume of the helium by a factor of 64, so it seems likely that they could get close to neutral buoyancy without using the vertical thrusters at all. The real problem will be with their claims that it will be able to land and take off without airports or ground support. I don't see how even the smallest model could manage station-keeping in even the lightest of breezes that wasn't coming from directly in front of the craft. You'll notice that the prototype does all its testing inside a closed hangar to avoid showing how ungainly it is.
ReplyDeleteIt's true that these ships are gonna get pushed around a lot more then normal, but I don't think it will be any more then what Ship captions need to deal with. I've worked with small ships before and we figured it out. Airships will need to do the same.
ReplyDeleteMost likely they will need to offload facing into the wind as you say, but in terms of ground support this thing will be far easier to land then anything else out there, you can land at any speed, so it realistically only needs a space that big enough for it to fit into.
I think you're looking at this the wrong way. For one, the other versions of the aeroscraft will likely use helium superheating from the engines. As any experienced airship pilot could tell you, even the effect of sunlight warming the top of the hull can drastically alter lift- in the USS Shenandoah's case, enough to regularly take off by day and land at night without venting helium or tossing ballast. I'm not sure exactly how much heating the Helium to, say, 80 to 100 degrees Celsius or so will impact the lift, but it could potentially increase lift by a third. This isn't anything unprecedented, either- the Breitling Orbiter 3 circumnavigation balloon used superheated helium.
ReplyDeleteThe second are the engines you list. If you had read aeros' own materials, they say over and over that they will have a hybrid drivetrain. Some engines- four to six of them- will be turboprops or some other form of jet engine, engaged for takeoff and landing and to reach high speeds. The other 2 or 3 engines- placed at the rear, in the ideal drag zone- will be diesels engaged for economical cruising. Just for example, the turboprops of a A400M Atlas weigh about two tons each, yet make over 11,000 shaft horsepower. To carry the analogy a bit further, you'd therefore need five of those engines to exceed your 54,000 horsepower requirement, a mere ten tons of engine. Or, put another way, 25% more engine than the Atlas. Yet the ML 86X carries 500 tons. The Atlas carries between... twenty and forty tons. With the engines themselves consuming approximately 0.39 pounds per shaft horsepower/hour, five of 'em will consume about ten tons of fuel per hour- assuming, of course, that the airship has all five of them engaged for some weird reason, and was ignoring the diesel economy engines.
So, just using a random turboprop, you can easily have a VTOL airship with over 55,000 horsepower that consumes about 10 tons per hour at WORST, not even counting the fact that the majority of the engines would be shut down in flight. And the engines only weigh 10 tons themselves. You posited a whopping 300 tons of engine, ALSO at about 10 tons of fuel per hour, and you had difficulty even CONCIEVING of an engine weight budget of 44 tons.
Have a little more faith in people. The guys at Aeros aren't novices. They know what they're doing.
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ReplyDeleteYou need to go back and get your GED and then go on to University and study engineering. From what you you wrote, it appears you are clueless.
ReplyDeletejjames129, you are completely right ! The team at Aeros had been looking, during many years, for all feasible solutions to make this fantastic dream become real ... and they are almost there ... hope to see the ML86X very soon !!!
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